Arthropod phylogeny: onychophoran brain organization suggests an archaic relationship with a chelicerate stem lineage

Abstract

Neuroanatomical studies have demonstrated that the architecture and organization among neuropils are highly conserved within any order of arthropods. The shapes of nerve cells and their neuropilar arrangements provide robust characters for phylogenetic analyses. Such analyses so far have agreed with molecular phylogenies in demonstrating that entomostracansCmalacostracans belong to a clade (Tetraconata) that includes the hexapods. However, relationships among what are considered to be paraphyletic groups or among the stem arthropods have not yet been satisfactorily resolved. The present parsimony analyses of independent neuroarchitectural characters from 27 arthropods and lobopods demonstrate relationships that are congruent with phylogenies derived from molecular studies, except for the status of the Onychophora. The present account describes the brain of the onychophoran Euperipatoides rowelli, demonstrating that the structure and arrangements of its neurons, cerebral neuropils and sensory centres are distinct from arrangements in the brains of mandibulates. Neuroanatomical evidence suggests that the organization of the onychophoran brain is similar to that of the brains of chelicerates.

Dangerous mating systems: Signal complexity, signal content and neural capacity in spiders

“…In insects, the mushroom body is suggested to be involved in numerous complex behaviors such as sensory integration, visual navigation, place memory, motor control, and learning and memory-particularly olfactory learning and memory (reviewed in Farris, 2005). Unfortunately, in contrast to the abundance of research conducted on insect mushroom body structure and function, relatively little is known about arachnid mushroom bodies (but see Strausfeld et al, 1998, Strausfeld et al, 2006: Strausfeld, 2012. In spiders, unlike other arachnids, the mushroom bodies appear to have assumed a role in visual processing; specifically receiving information from secondary eyes which function primarily in movement detection (Strausfeld, 2012).…”

Fine Structure of the Neuroganglia in the Central Nervous System of the Harvestman Leiobunum japonicum (Arachnida: Opiliones)

“…Accordingly, the CNS in L. japonicum is also located in the frontal portion of the prosoma and is made up of a large neural mass which consist of the upper supraesophageal ganglion and the lower subesophageal ganglion (Park & Moon, 2016). Since the Opiliones do not have antennae or abdominal appendages, the nervous system for controling the appendages are concentrated on the cephalothorax, and the absence of antennae implies the absence of a deutocerebrum as found in crustaceans and insects (Gullan & Cranston, 2010;Mittmann & Scholtz, 2003;Strausfeld et al, 2006). The supraesophageal ganglion of all arthropods was through to include three components -protocerebrum, deutocerebrum, and tritocerebrum.…”

Phylogenetisches Symposium Göttingen

“…11C, Dewel et al 1999) so that a polarization of these characters e. g. by comparison to Onychophora (Strausfeld et al 2006a, b) will soon be possible. − The anterior three neuromeres of the euarthropod nervous system are the protocerebrum (ocular segment), deutocerebrum (cheliceral segment in Chelicerata, first antennal segment in Mandibulata) and tritocerebrum (pedipalp segment in Chelicerata, second antennal segment in Crustacea, intercalary segment in Hexapoda).…”

“…The brain therefore provides a wealth of morphological features that can be analysed on a different level than the architecture of single individually identifiable neurons as described above, and the information obtained from analysing brain design is an important supplement for the phylogenetic data obtained from the ventral nerve cord (reviews Strausfeld et al 1995, Strausfeld 1998, Harzsch 2004a, Fanenbruck and Harzsch 2005, Harzsch 2006). Recent examples for neuroanatomical studies with a phylogenetic motivation have focused on the brain layout in Onychophora (Eriksson and Budd 2000, Eriksson et al 2003, Strausfeld et al 2006a, Tardigrada (Dewel and Dewel 1996, Dewel et al 1999), Chelicerata (Breidbach and Wegerhoff 1993, Mittmann and Scholtz 2003, Harzsch et al 2005b, and remipede crustaceans ( Fig. 5E; Fanenbruck et al 2004, Fanenbruck andHarzsch 2005) as well as on structures such as the central complex ( Fig.…”

“…Fanenbruck et al 2004, Harzsch 2004a, Fanenbruck and Harzsch 2005, Harzsch et al 2005a, Strausfeld 2005. Neurocharacters have also been evaluated in cladistic analyses (Strausfeld 1998, Strausfeld 2005, Strausfeld et al 2006a. Harzsch (2006) has attempted to reconstruct the neuronal characters in the ground patterns of the various arthropod groups and to polarize the character states as apomorphic versus plesiomorphic.…”